The present invention is directed to a connection between a cross member and a main member for a suspended ceiling support structure which has a plurality of main runners or members extending parallel to each other and cross-members extending between the main members or runners at spaced intervals. In particular, the connection allows for expansion of the cross-member which is created by an elevated temperature such as a fire so that the suspended ceiling support structure will be a fire-rated structure. Each of the members has an inverted T configuration with a pair of oppositely extending flanges connected by a web portion to a bead. The connection for attaching the cross-members to the main member comprises a tongue extending from the end of the cross-member through an elongated slot in the web of the main member. To hold the tongue in the slot the tongue is provided with a shoulder and an abutment surface which will engage the web adjacent the slot on opposite sides. In addition, the tongue is provided with another abutment surface adjacent an end which is received by an engagement surface of the adjacent tongue to hold the two members from opposite sides together.
Suspended ceiling support systems or structures which utilize a plurality of main runners and cross-members are shown in a number of U.S. patents and one such system is described in copending U.S. application Ser. No. 569,454, filed Jan. 9, 1984 and, which issued as U.S. Pat. No. 4,525,973 on July 2, 1985 and is assigned to the assignee of the present application. In the arrangement disclosed in this patent application, the beads on the edge of the flange of the cross-member are cut relative to the tongue so that when the tongue is inserted through a slot in the web of the main member, the bead is in contact with the bead of the main member as the edges of the end surfaces of the flanges of the cross-member are engaging the edges of the flanges of the main member. This arrangement will not allow for expansion at the connection due to increased temperatures which are caused by a fire.
In another type of construction for cross-members, it is known to provide an offset portion in the flanges of the cross-members at the end so that when the tongue is inserted in a slot in the web of the main member, the offset portion is received on the edge of the flange of the main member. Examples of this are disclosed in U.S. Pat. Nos. 3,312,488; 3,378,976; 3,921,363 and 4,317,641. Each of these patents have shoulders provided on the tongue which limit the depth of insertion of the tongue into the slot in the web of the main member. In the arrangement disclosed in U.S. Pat. No. 3,378,976, the shoulder is formed on an extension which will buckle when the ceiling framework is subjected to a large amount of heat to allow the tongue to extend further in as the flanges of the cross-member ride up over the flanges of the main member. In U.S. Pat. Nos. 3,921,363 and 4,317,641, to provide for fire rating, the shoulders are formed by tabs which will shear off to allow penetration of the tongue further into the slot due to expansion of the cross-member. In the arrangement in U.S. Pat. No. 3,312,488, the tongue is a separate member which is secured on the web of the cross-member and has two thicknesses with the shoulder being on one layer which engages projections extending into the aperture or slot. Due to the size of these projections, they will be sheared or bent out of the plane of the web when a certain force is applied by the tongue thereto. With this last-mentioned arrangement, added cost for providing the tongue occurs. With those arrangements having tabs that break off, they sometimes are accidentally broken off during handling and thus result in a damaged cross-member that cannot be used.